Comments on: Searching for the Sobrantehttps://oaklandgeology.wordpress.com/2012/06/08/searching-for-the-sobrante/
focused on, near and under Oakland, CaliforniaThu, 24 May 2018 02:50:41 +0000hourly1http://wordpress.com/By: Sara Webb-Schmitzhttps://oaklandgeology.wordpress.com/2012/06/08/searching-for-the-sobrante/#comment-13689
Thu, 16 Feb 2017 18:14:58 +0000http://oaklandgeology.wordpress.com/?p=1373#comment-13689I don’t know if you still read comments here, but I live in El Sobrante. At our neighborhood park (Lamoine Park), part of the hillside was cut away to create a flat space for the playground. At the top of that cutaway, my son and I found a layer of fragile sandstone (most of it crumbles or fractures with just a firm squeeze), and that layer is rife with small marine fossils–fan-shaped shells, spiral shells, etc. I was very curious about what this formation might be, and my amateur research led me to wonder if it was the Sobrante Formation. If you ever want to check it out, the park is located across the road from the May Valley Community Center (MVCC address: 3530 Morningside Dr, El Sobrante, CA 94803).

There is a fire engine play structure with a slide. Stand at the end of that slide and face up the hill. There are a couple of large pine trees slightly to your right at the top of the hill before the fence. Starting with the exposed rock around the trees’ roots and then stretching to the left for about 10 yards, we have found these rocks. It’s all exposed and eroding down the hill.

If you would like to see photos of the fossils, I can email them to you. It’s probably not the Sobrante Formation, but if it is, it is a lovely and easy spot to dig around and find fossils–shaded, not on a busy road, etc. If you do happen to know what this formation is, we’d be interested in finding out. We have some great science teachers at our elementary school who would probably love to take the kids on a quick walk up the hill for a geology lesson.

Many thanks!
Sara

[The geologic map says that locality is probably part of an unnamed sandstone unit of Miocene age. The Sobrante Formation isn’t very well defined. The rocks in Oakland were tentatively correlated with the Sobrante by Dorothy Radbruch in the 1960s. I haven’t found much about the actual Sobrante Formation, although the geologic map I use shows a Sobrante Sandstone in a few places in Contra Costa County.

If the outcrop is small, I think that fossil-hunting kids would strip it clean in short order. — Andrew]

]]>By: oaklandrockshttps://oaklandgeology.wordpress.com/2012/06/08/searching-for-the-sobrante/#comment-2941
Sat, 09 Jun 2012 04:15:43 +0000http://oaklandgeology.wordpress.com/?p=1373#comment-2941I was just up on Thorndale taking that narrow road up to Elverton and then Skyline. Didn’t know anyone else ever used the road. I definitely noticed the crumbling rock – infact ran over a few rocks. Had no idea that this was called Sobrante.
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